Software defined networking systems and methods via a path computation and control element

ABSTRACT

Software Defined Networking systems and methods are described via a Path Computation and Control Element (PCCE) that is based in part on a Path Computation Element (PCE). A common, simple interface is designed based on an existing PCE interface that allows a centralized entity (i.e., a Path Computation and Control Element or PCCE) to control the initiation of new connections or tunnels and by default to manage the state of these connections or tunnels once established. In particular, the systems and methods create an extension to the PCE architecture to allow a centralized application or applications to control the creation, rerouting and deletion of connections within a network.

FIELD OF THE INVENTION

Generally, the field of art of the present disclosure pertains tonetworking systems and methods, and more particularly, to SoftwareDefined Networking systems and methods via path computation and control.

BACKGROUND OF THE INVENTION

Automated connection control in optical or connection-oriented networksoperates currently with fully distributed control, where requests forconnections are made from the source node, either triggered by a clientrequest (switched connection (SC)) or by management system (softpermanent connection (SPC)). A client request can utilize a standarduser-network interface protocol such as have been defined in theInternet Engineering Task Force (IETF) or in the Optical InternetworkingForum (OIF), while management system interfaces are typically highlyequipment dependent, as the management interface needs to be tailored tomanage each device's unique set of characteristics.

Path Computation Elements (PCEs) are described, for example, in RFC 4655“A Path Computation Element (PCE)-Based Architecture,” (August 2006),the contents of which are incorporated by reference herein. Thisincludes another standardized interface that has been defined for pathcomputation, where the source node does not do its own path computationupon receiving a connection request (either SC or SPC) but makes a queryto the centralized PCE. The Path Computation Client (PCC) requests apath to a specified destination with some constraints such as connectiontype or bandwidth, and the PCE responds with a list of nodes and linksto be used, then the PCC creates the specified path using signaling.PCCs are also described, for example, in RFC 4655. The PCE wasoriginally defined to be stateless, that is, having no memory retainedafter a path query has been received and responded to. A new extensionto PCE now allows the PCE to retain state information, and in some casesaffect the state of an established connection, for which the source nodehas previously delegated control to the PCE. This involvessynchronization of the connection state between the PCC and PCE so thatthe PCE has an initial record of the connection state, then optionallydelegation of state control from the PCC to the PCE, and then stateupdates from either side, from the PCC to reflect any events such asfailures and from the PCE to reflect changes that it wants to make tothe connection such as rerouting or deleting.

Finally work on Software Defined Networks (SDN) calls for the ability tocentrally program provisioning of forwarding in the network in order formore flexible and precise control over network resources to support newservices. OpenFlow (www.openflow.org) is an implementation of this whichrequires a special OpenFlow interface from the controller to each switchin the network in order to provision the forwarding table at each switchalong a connection path in order to instantiate the forwarding behaviorneeded for the connection. OpenFlow is described, for example, in theOpenFlow Switch Speciation, Version 1.1.0 (February 2011), the contentsof which are incorporated by reference herein.

In the current state of the art, using distributed control plane, theestablishment of connections is typically disjointed, as for SCconnections there is no central coordination but each request isresponded to separately by a receiving source node, while for SPCconnections coordination of multiple connections is only possible withina limited span of control of a single management system, and does noteasily expand to handle multiple different vendors' equipment or evenmultiple types of equipment made by a single vendor, which may usedifferent management systems.

PCE allows centralization of path computation, but in its stateless modethe control of the connections themselves is still distributed to thesource node, while in stateful mode control can only be exerted by thePCE after the connection has been established and the source node hasdelegated control to the PCE. The PCE does not have any way to exertcontrol on the initial establishment of the connection, and must rely onthe source node to first request path computation and secondly delegatecontrol of the connection to the PCE. The source node can take backcontrol of the connection at any time. Also, OpenFlow/SDN fullycentralized control does not take advantage of existing distributedintelligence in the switch that provides greater efficiency andreliability than fully centralized control.

BRIEF SUMMARY OF THE INVENTION

The present disclosure overcomes the aforementioned limitations withSoftware Defined Networking systems and methods using a Path Computationand Control Element (PCCE). The PCCE is based in part on a PathComputation Element (PCE) with additional functionality of a centralizedentity controlling the initiation of new connections or tunnels andmanaging the state of the connections or tunnels once established. Inparticular, extensions are provided to the PCE architecture to allow acentralized application or applications to control the creation,rerouting and deletion of connections within a network. Compared toother mechanisms such as OpenFlow, the centralized controller is freefrom interacting with each node in the connection (instead relying onthe signaling intelligence in each node for distributed creation of theconnection). Because it is based in part on PCE technology, the PCCEtakes advantage of PCE infrastructure that has already beenstandardized, tested and implemented as an interface to networkelements.

In an exemplary embodiment, a path computation and control methodincludes receiving a request for a new connection in a network at a PathComputation and Control Element (PCCE); computing a path through thenetwork based on a network graph of current topology in the network andapplying computational constraints; sending an update message to one ofa source network element and a Path Computation Client (PCC) with thepath and a new connection identifier for the path, wherein the PCCE isconfigured to initiate and control creation of a connection based on thepath while directly interacting with the one of the source networkelement and the PCC; receiving a report message from the one of thesource network element and the PCC that the connection has been createdbased on the computed path; and updating the current topology based onthe report message. The path computation and control method can furtherinclude associating by the PCCE with the one of the source networkelement and the PCC based on one of a preconfigured list anddetermination based on the current topology. The path computation andcontrol method can further include receiving network topology updatesthrough a control plane operating in the network; and choosing a set ofnetwork elements in the network to be one of the source network elementand the PCC based on the current topology.

The path computation and control method can further include sending anopen message by the PCCE to the one of the source network element andthe PCC with inclusion of the Connection Initiator flag therein; andreceiving one of a KeepAlive response and an error indication from theone of the source network element and the PCC. The path computation andcontrol method can further include receiving the request for the newconnection at the PCCE from an application over a northbound interface;and using the northbound interface to convey network updates from thePCCE to the application. The update message can include a PathComputation Element (PCE) Communication Protocol update message forstateful PCE. The update message can include a flag to indicateInitiation Requested. The PCCE can be configured to provide the newconnection identifier as a unique identifier. The report message caninclude a Path Computation Element (PCE) Communication Protocol reportmessage from the one of the source network element and the PCC to thePCCE to indicate the connection is setup. The PCCE can be configured tooperate as a Path Computation Element (PCE) for conveying informationwith the one of the source network element and the PCC and to operate asa PCC for providing initiation functionality of the request. The PCCEcan rely upon a distributed control plane in the network to establishthe connection once the update message is sent to the one of the sourcenetwork element and the PCC.

In another exemplary embodiment, a network entity providing pathcomputation and control includes a network interface; a processor; andmemory storing instructions that, when executed, cause the processor to:receive a request for a new connection in a network; compute a paththrough the network based on a network graph of current topology in thenetwork and applying computational constraints; send, via the networkinterface, an update message to one of a source network element and aPath Computation Client (PCC) with the path and a new connectionidentifier for the path, wherein the network entity is configured toinitiate and control creation of a connection based on the path whiledirectly interacting with the one of the source network element and thenetwork entity; receive, via the network interface, a report messagefrom the one of the source network element and the PCC that theconnection has been created based on the computed path; and update thecurrent topology based on the report message. The instructions, whenexecuted, can further cause the processor to: associate with the one ofthe source network element and the PCC based on one of a preconfiguredlist and determination based on the current topology. The instructions,when executed, can further cause the processor to: receive networktopology updates through a control plane operating in the network; andchoose a set of network elements in the network to be one of the sourcenetwork element and the PCC based on the current topology.

The instructions, when executed, can further cause the processor to:send, via the network interface, an open message to the one of thesource network element and the PCC with inclusion of the ConnectionInitiator flag therein; and receive, via the network interface, one of aKeepAlive response and an error indication from the one of the sourcenetwork element and the PCC. The instructions, when executed, canfurther cause the processor to: receive, via the network interface, therequest for the new connection from an application over a northboundinterface; and use the northbound interface to convey network updates tothe application via the network interface. The update message caninclude a Path Computation Element (PCE) Communication Protocol updatemessage for stateful PCE; wherein the update message can include a flagto indicate Initiation Requested; and wherein the report message caninclude a Path Computation Element (PCE) Communication Protocol reportmessage from the one of the source network element and the PCC to thenetwork entity to indicate the connection is setup.

In yet another exemplary embodiment, a network includes a plurality ofnetwork elements communicatively coupled therebetween; a control planeoperating between the plurality of network elements; and a PathComputation and Control Element (PCCE) communicatively coupled to atleast one of the plurality of network elements; wherein the PCCE isconfigured to: receive a request for a new connection in the network;compute a path based on a network graph of current topology in thenetwork and applying computational constraints; send an update messageto one of a source network element and a Path Computation Client (PCC)with the path and a new connection identifier for the path, wherein thePCCE is configured to initiate and control creation of a connectionbased on the path while directly interacting with the one of the sourcenetwork element and the PCC; receive a report message from the one ofthe source network element and the PCC that the connection has beencreated based on the computed path; and update the current topologybased on the report message. The PCCE can be configured to operate as acombined stateful Path Computation Element (PCE) and Path ComputationClient (PCC) with an interface from an application for receiving therequest.

BRIEF DESCRIPTION OF THE DRAWING(S)

Exemplary and non-limiting embodiments of the present disclosure areillustrated and described herein with reference to various drawings, inwhich like reference numbers denote like method steps and/or systemcomponents, respectively, and in which:

FIGS. 1A-1B are network diagrams of a network with a client (FIG. 1A)and a management system (FIG. 1B) requesting connections;

FIG. 2 is a network diagram of a network of network elements with a PCCrequesting connections from a PCE;

FIGS. 3A-3C are network diagrams of a network with the PCE and the PCCfor stateful PCE;

FIG. 4 is a network diagram of a network with a Path Computation andControl Element (PCCE);

FIG. 5 is a flowchart of a PCCE initiation method;

FIG. 6 is a flowchart of a PCCE connection creation method;

FIG. 7 is a block diagram illustrates an exemplary implementation of aPCCE; and

FIG. 8 is a network diagram of the network of FIG. 4 using an OpenFlowcontroller in lieu of the PCCE.

DETAILED DESCRIPTION OF THE INVENTION

In various exemplary embodiments, the present disclosure relates toSoftware Defined Networking systems and methods via a Path Computationand Control Element (PCCE) that is based in part of a Path ComputationElement (PCE). In the systems and methods described herein, a common,simple interface is designed based on an existing PCE interface, butallowing a centralized entity (i.e., a Path Computation and ControlElement or PCCE) to control the initiation of new connections ortunnels, and by default also manage the state of these connections ortunnels once established. In particular, the systems and methods createan extension to the PCE architecture to allow a centralized applicationor applications to control the creation, rerouting and deletion ofconnections within a network. Compared to other mechanisms such asOpenFlow, the centralized controller (i.e., the PCCE) does not have tointeract with each node in the connection (instead relying on thesignaling intelligence in each node for distributed creation of theconnection). Because it is based on PCE technology, it takes advantageof PCE infrastructure that has already been standardized, tested andimplemented as an interface to network elements.

Referring to FIGS. 1A-1B, in exemplary embodiments, network diagramsillustrate a network 10 with a client 12 (FIG. 1A) and a managementsystem 14 (FIG. 1B) requesting connections. The network 10 includes aplurality of network elements 16 interconnected with one another. Thenetwork elements 16 can include, without limitation, optical networkelements, switches, routers, cross-connects, etc. configured to use acontrol plane for management thereof. In an exemplary embodiment, thenetwork elements 16 can include a nodal device that consolidates thefunctionality of a multi-service provisioning platform (MSPP), digitalcross connect (DCS), Ethernet and Optical Transport Network (OTN)switch, dense wave division multiplexed (DWDM) platform, etc. into asingle, high-capacity intelligent switching system providing Layer 0, 1,2, and/or 3 consolidation. In another exemplary embodiment, the networkelements 16 may include any of an OTN add/drop multiplexer (ADM),SONET/SDH ADM, a multi-service provisioning platform (MSPP), a digitalcross-connect (DCS), an optical cross-connect, a WDM/DWDM terminal, aswitch, a router, and the like.

Generally, the control plane includes software, processes, algorithms,etc. that control configurable features of the network 10, such asautomating discovery of the network elements 12, capacity on the links14, port availability on the network elements 12, connectivity betweenports; dissemination of topology and bandwidth information between thenetwork elements; calculation and creation of paths for connections;network level protection and restoration; and the like. Exemplarycontrol planes can include, without limitation, Automatically SwitchedOptical Network (ASON) as defined in inter alia G.8080/Y.1304,Architecture for the automatically switched optical network (ASON)(02/2005), the contents of which are herein incorporated by reference,and the like; Generalized Multi-Protocol Label Switching (GMPLS)Architecture as defined in inter alia Request for Comments: 3945(10/2004), the contents of which are herein incorporated; OpticalSignaling and Routing Protocol (OSRP) from Ciena Corporation which is anoptical routing protocol similar to PNNI (Private Network-to-NetworkInterface) and MPLS (Multiprotocol Label Switching); and the like. Thoseof ordinary skill in the art will recognize the network 10 and thecontrol plane may utilize any type of control plane for controlling thenetwork elements 16 and establishing connections therebetween.

GMPLS, for example, is a fully distributed control plane with eachnetwork element 16 sending data to a next network element 16 to create aconnection 18 in the network 10. FIG. 1A illustrates a switchedconnection (SC) created by the client 12. In particular, the client 12can include, without limitation, optical network elements, switches,routers, cross-connects, servers, etc. The client 12 is configured toinitiate a request for the connection 18 to one of the network elements16 via a User-Network Interface (UNI) protocol. The control plane inturn is configured to determine a path and use a signaling protocol toestablish the connection 18 in the network 10. FIG. 1B illustrates asemi-permanent connection (SPC) created by the management system 14. Themanagement system 14 can include, without limitation, a networkmanagement system (NMS), an element management system (EMS), anoperations support system (OSS), a craft interface (CI), a command lineinterface (CLI), etc. The management system 14 is configured tocommunicate to a source network element 16 for the connection 18, anduses network management interfaces and protocols.

Referring to FIG. 2, in an exemplary embodiment, a network diagramillustrates a network 20 of network elements 16A-16F with a PCE 22 and aPCC 24. The PCE 22 is an entity (e.g., component, application, ornetwork node) that is capable of computing a network path or route basedon a network graph and applying computational constraints. The PCE 22entity is an application that can be located within one of the networkelements 16 or a component, such as on server communicatively coupled tothe network elements 16. The PCC 24 is a client application requesting apath computation to be performed by the PCE 22. In addition to RFC 4655,PCEs and PCCs are defined in various RFC's from the IETF such as, forexample, RFC 4657 “Path Computation Element (PCE) Communication ProtocolGeneric Requirements,” RFC 4674 “Requirements for Path ComputationElement (PCE) Discovery,” RFC 4927 “Path Computation ElementCommunication Protocol (PCECP) Specific Requirements for Inter-Area MPLSand GMPLS Traffic Engineering,” RFC 5376 “Inter-AS Requirements for thePath Computation Element Communication Protocol (PCECP),” RFC 5394“Policy-Enabled Path Computation Framework,” RFC 5440 “Path ComputationElement (PCE) Communication Protocol (PCEP),” and the like, each ofwhich is incorporated by reference herein.

An exemplary advantage of the PCE 22 and the PCC 24 is that the PCE 24enables outside clients to obtain optimal paths in the network 20without having to know the full topology and the like of the network 20.To perform path computations, the PCE 22 stores the network 20 topologyand resource information in a database. To request path computationservices to a PCE, RFC 5440 defines the PCE Communication Protocol(PCEP) for communications between the PCC 24 and the PCE 22, or betweentwo PCEs. The PCC 24 can initiate a path computation request to the PCE22 through a Path Computation Request (PCReq) message, and then the PCE22 will return the computed route to the requesting PCC 24 in responseto a previously received PCReq message through a PCEP Path ComputationReply (PCRep) message. In the example of FIG. 2, the PCC 24 is at orcommunicatively coupled to the network element 16A and requests a pathfrom the network element 16A to a node 26 which is communicativelycoupled to the network element 16E. This request from the PCC 24 to thePCE 22 is via a PCReq message for the path and identifies thedestination (i.e., the node 26) and any constraints. The PCE 22 in turncomputes a path and returns an Explicit Route Object (ERO) to the PCC 24in a PCRep which is a sequence of nodes and links to be followed. Forexample, the ERO can include network elements 16A, 16B, 16C, 16E to thenode 26. The source network element 16A uses this information to createthe connection via signaling between the network elements 16.

Referring to FIGS. 3A-3C, in exemplary embodiments, network diagramsillustrate the network 20 with the PCE 22 and the PCC 24 for statefulPCE. As per RFC 4655, the PCE 22 can be stateless or stateful. Comparedto a stateless PCE, such as the PCE 22 in FIG. 2, a stateful PCE storesnot only the network state, but also the set of computed paths andreserved resources in use in the network 20. Note that [RFC4655] furtherspecifies that the database for the PCE 22 contains link state andbandwidth availability as distributed by the network elements 16 orcollected via other means. Even if such information can provide finergranularity and more details, it is not state information in the PCEcontext and so a model that uses it is still described as a statelessPCE. Stateful PCEs can be advantageous in many contexts, such as GMPLSnetworks, and require extensions to the PCEP.

FIGS. 3A-3C illustrate the PCE 22 as s stateful PCE. In FIG. 3A, the PCE22 performs state synchronization with the PCC 24 to obtaincharacteristics of the network 20. For example, the PCE 22 can requestan update with a message from the extensions to PCEP (PCUpd) and receivea response from the PCC 24 via a report message (PCRpt). The informationexchanged can include bandwidth (i.e., available, granularity, etc.) aswell as other characteristics (e.g., optical related constraints). InFIG. 3B, the PCC 24 is requesting a path for a connection 28 similar toFIG. 2. In FIG. 3C, the PCE 22 can modify the connection 28 forrerouting based on updated state conditions.

Referring to FIG. 4, in an exemplary embodiment, a network diagramillustrates a network 30 with a Path Computation and Control Element(PCCE) 32. The PCCE 32 can be realized in a similar fashion as the PCE22, i.e. an entity (e.g., component, application, or network node).Compared to the existing PCE architecture, the systems and methods allowthe PCCE 32 itself to initiate and control connections instead of havingto rely on the PCC 24 to request path computation and then delegatecontrol to the PCE 22. The PCCE 32 can itself check for support of PCCEconnection initiator functionality. At the same time, the systems andmethods takes advantage of the PCE protocol's existing ability to carryall of the information necessary to specify the path and characteristicsof a new connection, i.e. via the PCEP. Compared to existing distributedcontrol architectures, the systems and methods described herein are notdependent on the client 12 to initiate connections or on a networkmanagement interface for the management systems 14 to initiateconnections. Instead the PCCE 32 provides a northbound interface toapplications allowing the applications to request connectivity. The PCCE32 can from a central point and with knowledge of network topology andcurrent connections, compute an optimal path to support the desiredconnectivity based on criteria such as network utilization, diversityfrom existing paths, distribution of load evenly across the network, orother criteria.

In the current PCE protocol, the PCE 22 and PCC 24 establish anassociation and then the PCE 22 responds to path requests from the PCC24 with lists of nodes and links forming the recommended path for a newconnection. In Stateful PCE, the PCC 24 additionally can delegatecontrol over connections to the PCE 22, and the PCE 22 can cause changesto the connection such as rerouting its path or changing its state,e.g., causing the connection to be deleted. In the systems and methodsdescribed herein, the PCCE 32 initially establishes associations witheach PCC 24 within a domain and indicates that the association is forconnection initiation through the Connection Initiator flag in theassociation. The PCCE 32 may be configured with a list of PCCs 24 or itmay have access to network topology through the network routing orcontrol protocol and choose the set of network elements 16 to act asPCCs 24. For example, it may use network topology to determine all edgenetwork elements 16 in the network topology and choose these nodes aspotential PCCs 24 for connection initiation. If the network element 16is not capable of supporting functionality for PCCE 32 connectioninitiation, it may reject the association with an appropriate errorindication The PCCE 32 supports a northbound interface that allowsapplications to use the PCCE 32 to request connectivity from a source todestination without having to have detailed knowledge of the networktopology.

Once association has been established, and an application uses thenorthbound interface to request connectivity, the PCCE 32 computes adesirable path and requests connection establishment from the PCC 24 atthe source network element 16 for the connection (this could be ateither end of the connection path) using the PCUpdate message, againwith an Initiation Requested flag to indicate that the Update is for anew connection rather than an existing connection. The PCCE 32 creates aunique connection identifier incorporating its own PCE ID to distinguishfuture messages for the connection (the identifier must be unique to thePCCE 32 in order to avoid conflict with any connections initiated by thePCC 24 on its own). The PCUpdate message from the PCCE includes therequested path for the connection, determined from path computation atthe PCCE. Once the PCC 24 has successfully created the connectionthrough signaling, it returns a PCReport message to the PCCE 32reporting the state of the connection as “active”.

Referring to FIG. 5, in an exemplary embodiment, a flowchart illustratesa PCCE initiation method 50. The PCCE initiation method 50 can beimplemented by the PCCE 32 in the network 30 and in conjunction with thenetwork elements 16 and/or the PCC 24. The PCCE initiation method 50includes the PCCE determining which PCCs to contact based onconfiguration and/or topology information (step 52). As describedherein, the PCCE may be configured with a list of PCCs or it may haveaccess to network topology through the network routing protocol andchoose the set of network elements to act as PCCs. For example, the PCCEcan participate in receiving routing messages from the control planethereby having an updated topology of the network. With knowledge of thenetwork, the PCCE could determine which network elements are edge nodesas potential PCCs for connection initiation.

The PCCE sends a PCEP OPEN message with a connection initiator flag toeach of the PCCs (step 54). The OPEN message is sent to establish a PCEPsession between the PCCE and each of the PCCs. Specifically, the PCEPsession is established between the PCCE and the PCCs over a TransmissionControl Protocol (TCP) session. Each of the PCCs responds with aKeepAlive response to an error indication to the PCCE (step 54). Forexample, the OPEN message can include a KeepAlive time and a DeadTimertime. Assume that the PCCE and a PCC have set Keepalive=10 seconds andDeadTimer=40 seconds. This means that Keepalive messages (or any otherPCEP message) are sent every 10 seconds and that it can be declared thatthe PCEP session is down if no PCEP message has been received within any40-second period. Generally, the PCCE initiation method 50 is used forthe PCCE to establish PCEP sessions with the network elements 16 forfuture connection requests.

Referring to FIG. 6, in an exemplary embodiment, a flowchart illustratesa PCCE connection creation method 60. The PCCE connection creationmethod 60 can be implemented by the PCCE 32 in the network 30 and inconjunction with the network elements 16 and/or the PCC 24. Further, thePCCE connection creation method 60 can be used with the PCCE initiationmethod 50. The PCCE receive a request from an application to create aconnection (step 62). In particular, applications are configured torequest connections from the PCCE, such as using a northbound interfaceto the PCCE. Exemplary applications include, without limitation,clients, management systems, network elements, network elements in otherdomains, PCEs, other PCCEs, etc.

The PCCE computes a path through the network to support the requestedconnectivity in the request (step 64). Here, the PCCE can operate in asimilar fashion as a stateful PCE with up-to-date knowledge of thenetwork topology and available bandwidth in a PCCE database. The PCCEcan perform path computation in similar manner as a PCE. The PCCE sendsa PCEP UPDATE message with an initiate flag to the associated PCC alongwith a new connection ID (step 66). This can include the path, such asvia an ERO. The associated PCC can be the source node of the newconnection. The PCC creates the requested connection via signaling,using the path provided by the PCCE (step 68). For example, thePCC/source node can use the control plane to set up the connection. ThePCC sends a PCEP REPORT message to the PCCE indicating the connectionhas been created (step 70). Here, the PCC is sending the REPORT messageto maintain the proper state in the PCCE. The PCCE then notifies theapplication that the connectivity is available (step 72).

The PCCE systems and methods described here are a novel concept that hasnot been explored in the current work on PCE, it has significantadvantages for allowing network operators to control and coordinateconnections within their network both during their initial establishmentand during the active lifetime of the connection. Various unique aspectsof the PCCE systems and methods include, without limitation, theinitiation of association by the PCCE based on configuration or topologyinformation, inclusion of the Connection Initiator flag in theassociation, additional error indication if the PCCE connectioninitiation is not supported, support of a northbound interface from thePCCE to allow applications to indicate need for new connectivity fromsource to destination (interface can also convey information from PCCEto applications on network topology, use of the PC UPDATE message fromthe PCCE to create a new connection, flag to indicate InitiationRequested in the PC UPDATE message, procedure for creating a uniqueconnection identifier, and use of the PC REPORT message to indicateconnection complete.

Referring to FIG. 7, in an exemplary embodiment, a block diagramillustrates an exemplary implementation of the PCCE 32. The PCCE 32 canbe a digital computer that, in terms of hardware architecture, generallyincludes a processor 102, input/output (I/O) interfaces 104, a networkinterface 106, a data store 108, and memory 110. It should beappreciated by those of ordinary skill in the art that FIG. 7 depictsthe PCCE 32 in an oversimplified manner, and a practical embodiment mayinclude additional components and suitably configured processing logicto support known or conventional operating features that are notdescribed in detail herein. The components 102, 104, 106, 108, and 110)are communicatively coupled via a local interface 112. The localinterface 112 can be, for example but not limited to, one or more busesor other wired or wireless connections, as is known in the art. Thelocal interface 112 can have additional elements, which are omitted forsimplicity, such as controllers, buffers (caches), drivers, repeaters,and receivers, among many others, to enable communications. Further, thelocal interface 112 can include address, control, and/or dataconnections to enable appropriate communications among theaforementioned components.

The processor 102 is a hardware device for executing softwareinstructions. The processor 102 can be any custom made or commerciallyavailable processor, a central processing unit (CPU), an auxiliaryprocessor among several processors associated with the PCCE 32, asemiconductor-based microprocessor (in the form of a microchip or chipset), or generally any device for executing software instructions. Whenthe PCCE 32 is in operation, the processor 102 is configured to executesoftware stored within the memory 110, to communicate data to and fromthe memory 110, and to generally control operations of the PCCE 32pursuant to the software instructions. The I/O interfaces 104 can beused to receive user input from and/or for providing system output toone or more devices or components. User input can be provided via, forexample, a keyboard, touch pad, and/or a mouse. System output can beprovided via a display device and a printer (not shown). I/O interfaces104 can include, for example, a serial port, a parallel port, a smallcomputer system interface (SCSI), a serial ATA (SATA), a fibre channel,Infiniband, iSCSI, a PCI Express interface (PCI-x), an infrared (IR)interface, a radio frequency (RF) interface, and/or a universal serialbus (USB) interface.

The network interface 106 can be used to enable the PCCE 32 tocommunicate on a network, such as to communicate with the PCC 24, theapplication, any of the network elements 16, etc. The network interface106 can include, for example, an Ethernet card or adapter (e.g.,10BaseT, Fast Ethernet, Gigabit Ethernet, 10 GbE) or a wireless localarea network (WLAN) card or adapter (e.g., 802.11a/b/g/n). The networkinterface 106 can include address, control, and/or data connections toenable appropriate communications on the network. For example, PCEPsessions can be maintained by the PCCE 32 and the PCC over TCP throughthe network interface 106. The data store 108 can be used to store data.The data store 108 can include any of volatile memory elements (e.g.,random access memory (RAM, such as DRAM, SRAM, SDRAM, and the like)),nonvolatile memory elements (e.g., ROM, hard drive, tape, CDROM, and thelike), and combinations thereof. Moreover, the data store 108 canincorporate electronic, magnetic, optical, and/or other types of storagemedia. The data store 108 can be used to store a PCCE database thatmaintains state information for any associated network.

The memory 110 can include any of volatile memory elements (e.g., randomaccess memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), nonvolatilememory elements (e.g., ROM, hard drive, tape, CDROM, etc.), andcombinations thereof. Moreover, the memory 110 can incorporateelectronic, magnetic, optical, and/or other types of storage media. Notethat the memory 110 can have a distributed architecture, where variouscomponents are situated remotely from one another, but can be accessedby the processor 102. The software in memory 110 can include one or moresoftware programs, each of which includes an ordered listing ofexecutable instructions for implementing logical functions. The softwarein the memory 110 includes a suitable operating system (O/S) 114 and oneor more programs 116. The operating system 114 essentially controls theexecution of other computer programs, such as the one or more programs116, and provides scheduling, input-output control, file and datamanagement, memory management, and communication control and relatedservices. The one or more programs 116 may be configured to implementthe various processes, algorithms, methods, techniques, etc. describedherein.

In conjunction with the PCCE 32, the PCCE initiation method 50, and thePCCE connection creation method 60, it will be appreciated that someexemplary embodiments described herein may include one or more genericor specialized processors (“one or more processors”) such asmicroprocessors, digital signal processors, customized processors, andfield programmable gate arrays (FPGAs) and unique stored programinstructions (including both software and firmware) that control the oneor more processors to implement, in conjunction with certainnon-processor circuits, some, most, or all of the functions of themethods and/or systems described herein. Alternatively, some or allfunctions may be implemented by a state machine that has no storedprogram instructions, or in one or more application specific integratedcircuits (ASICs), in which each function or some combinations of certainof the functions are implemented as custom logic. Of course, acombination of the aforementioned approaches may be used. Moreover, someexemplary embodiments may be implemented as a non-transitorycomputer-readable storage medium having computer readable code storedthereon for programming a computer, server, appliance, device, etc. eachof which may include a processor to perform methods as described andclaimed herein. Examples of such computer-readable storage mediumsinclude, but are not limited to, a hard disk, an optical storage device,a magnetic storage device, a ROM (Read Only Memory), a PROM(Programmable Read Only Memory), an EPROM (Erasable Programmable ReadOnly Memory), an EEPROM (Electrically Erasable Programmable Read OnlyMemory), Flash memory, and the like. When stored in the non-transitorycomputer readable medium, software can include instructions executableby a processor that, in response to such execution, cause a processor orany other circuitry to perform a set of operations, steps, methods,processes, algorithms, etc.

Referring to FIG. 8, a network diagram illustrates the network 30 usingan OpenFlow controller 150 in lieu of the PCCE 32. In particular, FIG. 8can be contrast with the PCCE 32 in FIG. 4. In OpenFlow as shown in FIG.8, a special OpenFlow interface is required from the controller 150 toeach network element 16 in the network 30 in order to provision theforwarding table at each network element 16 along a connection path inorder to instantiate the forwarding behavior needed for the connection.Thus, OpenFlow is a centralized control technique that does not takeadvantage of existing distributed intelligence in the network elements16 that provides greater efficiency and reliability than fullycentralized control. The PCCE 32 seeks to combine several features ofOpenFlow, PCEs, and distributed control planes for combining theprovisioning of forwarding tables with a “tunnel” creation mechanism.The PCCE 32 creates an extension to the PCE architecture to allow acentralized application or applications to control the creation,rerouting and deletion of connections within the network 30. Compared toOpenFlow, the PCCE 32 is freed from interacting with each networkelement 16 in the connection (instead relying on the signalingintelligence in each network element 16 and the associated control planefor distributed creation of the connection). That is, the PCCE 32 isless resource intensive by leveraging the distributed control features.Because it is based on PCE technology, the PCCE takes advantage of PCEinfrastructure that has already been standardized, tested andimplemented as an interface to network elements.

Although the present disclosure has been illustrated and describedherein with reference to preferred embodiments and specific examplesthereof, it will be readily apparent to those of ordinary skill in theart that other embodiments and examples may perform similar functionsand/or achieve like results. All such equivalent embodiments andexamples are within the spirit and scope of the present disclosure andare intended to be covered by the following claims.

What is claimed is:
 1. A path computation and control method,comprising: receiving a request for a new connection in a network at aPath Computation and Control Element (PCCE); computing a path throughthe network based on a network graph of current topology in the networkand applying computational constraints; sending an update message to oneof a source network element and a Path Computation Client (PCC) with thepath and a new connection identifier for the path, wherein the PCCE isconfigured to initiate and control creation of a connection based on thepath while directly interacting with the one of the source networkelement and the PCC; receiving a report message from the one of thesource network element and the PCC that the connection has been createdbased on the computed path; and updating the current topology based onthe report message.
 2. The path computation and control method of claim1, further comprising: associating by the PCCE with the one of thesource network element and the PCC based on one of a preconfigured listand determination based on the current topology.
 3. The path computationand control method of claim 2, further comprising: receiving networktopology updates through a control plane operating in the network; andchoosing a set of network elements in the network to be one of thesource network element and the PCC based on the current topology.
 4. Thepath computation and control method of claim 1, further comprising:sending an open message by the PCCE to the one of the source networkelement and the PCC with inclusion of the Connection Initiator flagtherein; and receiving one of a KeepAlive response and an errorindication from the one of the source network element and the PCC. 5.The path computation and control method of claim 1, further comprising:receiving the request for the new connection at the PCCE from anapplication over a northbound interface; and using the northboundinterface to convey network updates from the PCCE to the application. 6.The path computation and control method of claim 1, wherein the updatemessage comprises a Path Computation Element (PCE) CommunicationProtocol update message for stateful PCE.
 7. The path computation andcontrol method of claim 6, wherein the update message comprises a flagto indicate Initiation Requested.
 8. The path computation and controlmethod of claim 1, wherein the PCCE is configured to provide the newconnection identifier as a unique identifier.
 9. The path computationand control method of claim 1, wherein the report message comprises aPath Computation Element (PCE) Communication Protocol report messagefrom the one of the source network element and the PCC to the PCCE toindicate the connection is setup.
 10. The path computation and controlmethod of claim 1, wherein the PCCE is configured to operate as a PathComputation Element (PCE) for conveying information with the one of thesource network element and the PCC and to operate as a PCC for providinginitiation functionality of the request.
 11. The path computation andcontrol method of claim 1, wherein the PCCE relies upon a distributedcontrol plane in the network to establish the connection once the updatemessage is sent to the one of the source network element and the PCC.12. A network entity providing path computation and control, comprising:a network interface; a processor; and memory storing instructions that,when executed, cause the processor to: receive a request for a newconnection in a network; compute a path through the network based on anetwork graph of current topology in the network and applyingcomputational constraints; send, via the network interface, an updatemessage to one of a source network element and a Path Computation Client(PCC) with the path and a new connection identifier for the path,wherein the network entity is configured to initiate and controlcreation of a connection based on the path while directly interactingwith the one of the source network element and the network entity;receive, via the network interface, a report message from the one of thesource network element and the PCC that the connection has been createdbased on the computed path; and update the current topology based on thereport message.
 13. The network entity of claim 12, wherein theinstructions, when executed, further cause the processor to: associatewith the one of the source network element and the PCC based on one of apreconfigured list and determination based on the current topology. 14.The network entity of claim 13, wherein the instructions, when executed,further cause the processor to: receive network topology updates througha control plane operating in the network; and choose a set of networkelements in the network to be one of the source network element and thePCC based on the current topology.
 15. The network entity of claim 12,wherein the instructions, when executed, further cause the processor to:send, via the network interface, an open message to the one of thesource network element and the PCC with inclusion of the ConnectionInitiator flag therein; and receive, via the network interface, one of aKeepAlive response and an error indication from the one of the sourcenetwork element and the PCC.
 16. The network entity of claim 12, whereinthe instructions, when executed, further cause the processor to:receive, via the network interface, the request for the new connectionfrom an application over a northbound interface; and use the northboundinterface to convey network updates to the application via the networkinterface.
 17. The network entity of claim 12, wherein the updatemessage comprises a Path Computation Element (PCE) CommunicationProtocol update message for stateful PCE; wherein the update messagecomprises a flag to indicate Initiation Requested; and wherein thereport message comprises a Path Computation Element (PCE) CommunicationProtocol report message from the one of the source network element andthe PCC to the network entity to indicate the connection is setup.
 18. Anetwork, comprising: a plurality of network elements communicativelycoupled therebetween; a control plane operating between the plurality ofnetwork elements; and a Path Computation and Control Element (PCCE)communicatively coupled to at least one of the plurality of networkelements; wherein the PCCE is configured to: receive a request for a newconnection in the network; compute a path based on a network graph ofcurrent topology in the network and applying computational constraints;send an update message to one of a source network element and a PathComputation Client (PCC) with the path and a new connection identifierfor the path, wherein the PCCE is configured to initiate and controlcreation of a connection based on the path while directly interactingwith the one of the source network element and the PCC; receive a reportmessage from the one of the source network element and the PCC that theconnection has been created based on the computed path; and update thecurrent topology based on the report message.
 19. The network of claim18, wherein the PCCE is configured to operate as a combined statefulPath Computation Element (PCE) and Path Computation Client (PCC) with aninterface from an application for receiving the request.